JP2013526004A - Contaminant particle removal system, lithographic apparatus, contaminant particle removal method, and device manufacturing method - Google Patents

Abstract

EUV in which at least a first AC voltage is supplied as a first stage of a voltage regime to at least one pair of electrodes opposite the path of the EUV radiation beam and a DC voltage is supplied to the electrodes as a second stage of the voltage regime A system is provided for removing contaminant particles from the path of the radiation beam.
[Selection figure] None

Description

(Cross-reference to related applications)
[0001] This application is filed on March 12, 2010 and claims the benefit of US Provisional Application No. 61 / 313,507, which is incorporated herein by reference in its entirety. Furthermore, it claims the benefit of US Provisional Application No. 61 / 348,521, filed May 26, 2010, which is incorporated herein by reference in its entirety.

The present invention relates to a system for removing contaminant particles from a path of an EUV radiation beam, a lithographic apparatus, a method for removing contaminant particles from a path of an EUV radiation beam, and a device manufacturing method.

[0003] A lithographic apparatus is a machine that applies a desired pattern onto a substrate, usually onto a target portion of the substrate. A lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In such cases, a patterning device, alternatively referred to as a mask or reticle, can be used to generate a circuit pattern to be formed on an individual layer of the IC. This pattern can be transferred onto a target portion (eg including part of, one, or several dies) on a substrate (eg a silicon wafer). The pattern is usually transferred by imaging onto a layer of radiation sensitive material (resist) provided on the substrate. In general, a single substrate will contain a network of adjacent target portions that are successively patterned.

[0004] Lithography is widely recognized as one of the major steps in fabricating ICs and other devices and / or structures. However, as the dimensions of features manufactured using lithography become finer, lithography has become a more critical factor to enable the manufacture of small ICs or other devices and / or structures. Yes.

[0005] A theoretical estimate of the limit of pattern printing is obtained by Rayleigh resolution criteria as shown in equation (1).

Where λ is the wavelength of radiation used, NA is the numerical aperture of the projection system used to print the pattern, k1 is a process dependent adjustment factor, also called the Rayleigh constant, and CD is the feature size of the feature to be printed (Ie critical dimension). From equation (1), it can be seen that reduction of the minimum printable size of a feature can be achieved in three ways. That is, by shortening the exposure wavelength λ, by increasing the numerical aperture NA, or by decreasing the value of k1.

[0006] To shorten the exposure wavelength and reduce the minimum printable size, it has been proposed to use an extreme ultraviolet (EUV) radiation source. EUV radiation is electromagnetic radiation having a wavelength in the range of 5-20 nm, for example in the range of 13-14 nm. Furthermore, it has been proposed that EUV radiation with a wavelength of less than 10 nm, for example in the range of 5-10 nm, such as 6.7 nm or 6.8 nm, can be used. Such radiation is called extreme ultraviolet radiation or soft x-ray radiation. Possible radiation sources include, for example, laser-produced plasma radiation sources, discharge plasma radiation sources, or radiation sources based on synchrotron radiation provided by electron storage rings.

[0007] EUV radiation can be generated using a plasma. A radiation system for generating EUV radiation may include a laser that excites fuel to provide a plasma, and a source collector module for containment of the plasma. The plasma can be generated, for example, by directing a laser beam or a suitable gas or vapor flow such as Xe gas or Li vapor to a fuel such as a suitable material (eg tin). The resulting plasma emits output radiation, such as EUV radiation, which is collected using a radiation collector. The radiation collector may be a mirrored normal incidence collector that receives radiation and focuses the radiation into the beam. The source collector module may include a closed structure or chamber that provides a vacuum environment to support the plasma. Such radiation systems are commonly referred to as laser produced plasma (LPP) radiation sources.

[0008] A problem with such systems is that the particles of fuel material are likely to be released with the radiation and may travel through the device at high or low speeds. When these particles contaminate optical surfaces such as mirror lenses and reticles, the performance of the device is degraded.

[0009] In some situations, photoelectric charging may not be sufficient to deflect all particles. Yet another problem arises when trying to utilize this technique in the hydrogen environment. In the presence of gas (H ₂ ), a pulse of EUV radiation generates a conductive hydrogen plasma. When this H ₂ plasma (generated by the EUV beam) is present in the region between the capacitor plates, the applied electric field is shielded by the plasma and does not deflect the particles. Furthermore, the plasma gradually applies a negative charge to the particles and erases the positive charge of the photoelectric effect.

[0010] Therefore, what is needed is an effective system and method that provides an alternative system for contaminant particle removal that is suitable for EUV apparatus in an atmosphere such as hydrogen.

[0011] In one embodiment of the present invention, at least one pair of electrodes provided on opposite sides of the EUV beam path and a controlled voltage is provided between the at least one pair of electrodes. A system is provided for removing contaminant particles from an EUV radiation path in a lithographic apparatus, including a voltage source. The system includes a controller configured to control a voltage supplied between at least one pair of electrodes, the controller configured to provide a voltage regime between the electrodes, wherein the regime is an alternating current (“AC”). ) Including a first stage in which a voltage is supplied to the pair of electrodes and a second stage in which a direct current (“DC”) voltage is supplied to the pair of electrodes.

[0012] In an embodiment of the invention, the system further provides a lithographic apparatus incorporating one or more such systems for removing contaminant particles.

[0013] In an embodiment of the present invention, a method of removing contaminant particles from a path of an EUV radiation beam in a lithographic apparatus, comprising at least a pair of electrodes on the opposite side of the path of the EUV radiation beam; Comprising a voltage regime between a pair of electrodes, the regime comprising: a first stage in which an AC voltage is supplied to the pair of electrodes; and a second stage in which a DC voltage is supplied to the electrodes. Is provided.

[0014] In an embodiment of the present invention, a device manufacturing method such as a semiconductor device is provided using the contaminant removal method.

[0015] Further embodiments, features and advantages of the present invention, as well as the structure and operation of the various embodiments of the present invention, are described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited to the specific embodiments described herein. Such embodiments are described herein for illustrative purposes only. Based on the teachings contained herein, those skilled in the art will readily perceive additional embodiments.

[0016] Embodiments of the present invention will now be described with reference to the accompanying schematic drawings in which corresponding reference numerals indicate corresponding parts, which are by way of illustration only. Furthermore, the accompanying drawings, which are incorporated in and form a part of this specification, illustrate the invention and, together with the description, further explain the principles of the invention and enable those skilled in the art to make and use the invention. Work.
[0017] Figure 1 schematically depicts a lithographic apparatus according to an embodiment of the invention; [0018] FIG. 2 is a more detailed view of an apparatus 100 according to an embodiment of the invention. [0019] FIG. 3 illustrates an alternative EUV radiation source that may be used with the apparatus of FIGS. [0020] Figure 1 depicts a modified lithographic apparatus according to an embodiment of the invention. [0021] FIG. 6 illustrates an embodiment of a system for removing contaminant particles according to an embodiment of the invention. [0022] FIG. 6 is a graph comparing the performance of previously known systems for removing contaminant particles in a system according to an embodiment of the present invention. [0022] FIG. 6 is a graph comparing the performance of previously known systems for removing contaminant particles in a system according to an embodiment of the present invention. [0023] FIG. 6 illustrates an alternative embodiment of a system for removing contaminant particles according to an embodiment of the invention. [0024] FIG. 9 is a graph comparing the performance of the system shown in FIG. 8 for particles with high and low secondary electron emission coefficients, respectively, according to an embodiment of the present invention. [0024] FIG. 9 is a graph comparing the performance of the system shown in FIG. 8 for particles of high and low secondary electron emission coefficients, respectively, according to an embodiment of the present invention.

[0025] The features and advantages of the present invention will become more apparent upon reading the following description with reference to the drawings, in which like reference numerals consistently identify corresponding elements. In the drawings, like numerals generally indicate elements that are identical, have similar functions, and / or have similar structures.

[0026] This specification discloses one or more embodiments that incorporate the features of this invention. The disclosed embodiments are merely illustrative of the invention. The scope of the invention is not limited to the disclosed embodiments. The invention is defined by the claims appended hereto.

[0027] Reference to the described embodiment, and "one embodiment", "an embodiment", "exemplary embodiment", etc. herein, indicates that the described embodiment has the specific features, structures Or that a particular feature, structure, or characteristic may not necessarily be included in each embodiment. Moreover, such phrases are not necessarily referring to the same embodiment. In addition, when describing a particular feature, structure, or characteristic in connection with an embodiment, such feature, structure, or characteristic, whether explicitly described or not, is described. It is understood that it is within the knowledge of those skilled in the art to perform in the context of other embodiments.

[0028] Embodiments of the invention may be implemented in hardware, firmware, software, or any combination thereof. Embodiments of the invention can also be implemented as instructions stored on a machine-readable medium that can be read and executed by one or more processors. A machine-readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (eg, a computing device). For example, machine-readable media can be read-only memory (ROM), random access memory (RAM), magnetic disk storage media, optical storage media, flash memory devices, electrical, optical, acoustic or other forms of propagated signals (eg, carrier waves) , Infrared signals, digital signals, etc.), and others. Further, firmware, software, routines, instructions may be described herein as performing certain actions. However, such a description is for convenience only and such an action may actually be the result of a computing device, processor, controller, or other device executing firmware, software, routines, instructions, etc. I want to be recognized.

[0029] According to an embodiment of the invention, Figure 1 schematically depicts a lithographic apparatus 100 including a source collector module SO according to an embodiment of the invention. The apparatus is constructed to support an illumination system (illuminator) IL configured to condition a radiation beam B (eg EUV radiation) and a patterning device (eg mask or reticle) MA, And a support structure (eg, mask table) MT connected to the first positioner PM configured to be accurately positioned. The lithographic apparatus 100 is also configured to hold a substrate (eg, a resist coated wafer) W and is connected to a second positioner PW configured to accurately position the substrate (eg, a wafer). A projection system configured to project a pattern imparted to the radiation beam B by the patterning device MA onto a table WT and a target portion C of the substrate W (e.g. including one or more dies) (e.g. Reflective projection system) PS.

[0030] The illumination system includes various types of optical components, such as refractive, reflective, magnetic, electromagnetic, electrostatic, etc. optical components, or any combination thereof, for directing, shaping or controlling radiation. You may go out.

[0031] The support structure MT holds the patterning device MA in a manner that depends on conditions such as the orientation of the patterning device MA, the design of the lithographic apparatus, for example, whether or not the patterning device is held in a vacuum environment. The support structure can use mechanical, vacuum, electrostatic or other clamping techniques to hold the patterning device. The support structure may be a frame or a table, for example, and may be fixed or movable as required. The support structure may ensure that the patterning device is at a desired position, for example with respect to the projection system.

[0032] The term "patterning device" should be construed broadly to refer to any device that can be used to pattern a cross-section of a radiation beam so as to generate a pattern in a target portion of a substrate. is there. The pattern imparted to the radiation beam corresponds to a particular functional layer in a device being created in the target portion, such as an integrated circuit.

[0033] The patterning device may be transmissive or reflective. Examples of patterning devices include masks, programmable mirror arrays, and programmable LCD panels. Masks are well known in lithography, and include mask types such as binary masks, Levenson phase shift masks, attenuated phase shift masks, and various hybrid mask types. It is. As an example of a programmable mirror array, a matrix array of small mirrors is used, each of which can be individually tilted to reflect the incoming radiation beam in a different direction. The tilted mirror imparts a pattern to the radiation beam reflected by the mirror matrix.

[0034] As used herein, the term "projection system" should be broadly construed as encompassing various types of projection systems and is suitable for the exposure radiation used as well as the illumination system. Or refraction, reflection, magnetic, electromagnetic, electrostatic or other types of optical components, or combinations thereof, suitable for other factors such as the use of vacuum. Since other gases can absorb excess radiation, it is desirable to use a vacuum for EUV radiation. Therefore, a vacuum environment may be provided in the entire beam path using a vacuum wall and a vacuum pump.

[0035] In this embodiment, for example, the apparatus is of a reflective type (eg using a reflective mask).

[0036] The lithographic apparatus may be of a type having two (dual stage) or more substrate tables and, for example, two or more mask tables. In such “multi-stage” machines, additional tables can be used in parallel, or prepared on one or more tables while one or more other tables are used for exposure. Steps can be performed.

Referring to FIG. 1, the illuminator IL receives an extreme ultraviolet radiation beam from a radiation source collector module SO. The method of generating EUV light includes converting the material to a plasma state having at least one element, such as xenon, lithium or tin, having one or more emission lines within the EUV range, It is not limited to this. One such method, often referred to as laser-produced plasma (“LPP”), involves irradiating the required plasma by irradiating a droplet, stream, or cluster of material having the required line-emitting element with a laser beam. Can be generated. The source collector module SO may be part of an EUV radiation system that includes a laser not shown in FIG. 1 to provide a laser beam that excites the fuel. The resulting plasma emits output radiation, such as EUV radiation, which is collected using a radiation collector disposed within the source collector module. If, for example, a CO2 laser is used to provide a laser beam for fuel excitation, the laser and the source collector module may be separate elements.

[0038] In such a case, the laser is not considered to form part of the lithographic apparatus, and the radiation beam is emitted from the laser using, for example, a beam delivery system comprising a suitable guiding mirror and / or beam expander. Sent to the source collector module. In other cases the source may be an integral part of the source collector module, for example when the source is a discharge produced plasma EUV generator often referred to as a DPP source.

[0039] The illuminator IL may include an adjuster for adjusting the angular intensity distribution of the radiation beam. In general, at least the outer and / or inner radius range (commonly referred to as σ-outer and σ-inner, respectively) of the intensity distribution at the pupil plane of the illuminator can be adjusted. Furthermore, the illuminator IL may comprise various other components such as faceted fields and pupil mirror devices. An illuminator may be used to adjust the radiation beam to obtain the desired uniformity and intensity distribution in the cross section.

[0040] The radiation beam B is incident on the patterning device (eg, mask) MA, which is held on the support structure (eg, mask table) MT, and is patterned by the patterning device. After reflection on the patterning device (eg mask) MA, the radiation beam B passes through the projection system PS, which focuses the beam onto the target portion C of the substrate W. Using the second positioner PW and the position sensor PS2 (eg interferometer device, linear encoder or capacitive sensor), the substrate table WT is accurate so that, for example, various target portions C can be positioned in the path of the radiation beam B. Can be moved to. Similarly, the patterning device (eg mask) MA can be accurately positioned with respect to the path of the radiation beam B using the first positioner PM and another position sensor PS1. Patterning device (eg mask) MA and substrate W may be aligned using mask alignment marks M1, M2 and substrate alignment marks P1, P2.

The illustrated lithographic apparatus can be used in at least one of the following modes:
1. In step mode, the support structure (eg mask table) MT and the substrate table WT are basically kept stationary, while the entire pattern imparted to the radiation beam is projected onto the target portion C at one time (ie Single static exposure). Next, the substrate table WT is moved in the X and / or Y direction so that another target portion C can be exposed.
2. In scan mode, the support structure (eg mask table) MT and the substrate table WT are scanned synchronously while a pattern imparted to the radiation beam is projected onto a target portion C (ie, a single dynamic exposure). The speed and direction of the substrate table WT relative to the support structure (eg mask table) MT can be determined by the enlargement (reduction) and image reversal characteristics of the projection system PS.
3. In another mode, the support structure (eg, mask table) MT is held essentially stationary with the programmable patterning device held in place to move or scan the substrate table WT while moving the pattern imparted to the radiation beam to the target portion. Project to C. In this mode, a pulsed radiation source is typically used to update the programmable patterning device as needed each time the substrate table WT is moved or between successive radiation pulses during a scan. This mode of operation can be readily applied to maskless lithography that utilizes programmable patterning device, such as a programmable mirror array of a type as referred to above.

[0042] Combinations and / or variations on the above described modes of use or entirely different modes of use may also be employed.

[0043] According to an embodiment of the invention, FIG. 2 shows in more detail an apparatus 100 that includes a source collector module SO, an illumination system IL, and a projection system PS. The radiation source collector module SO is constructed and arranged so that a vacuum environment can be maintained in the closed structure 220 of the radiation source collector module SO. The EUV radiation emitting plasma 210 can be formed by a discharge generated plasma source. EUV radiation can be generated by a suitable gas or vapor, such as, for example, Xe gas, Li vapor, or Sn vapor, and a very hot plasma 210 is generated to emit radiation in the EUV range of the electromagnetic spectrum. The very hot plasma 210 is generated, for example, by a discharge that produces an at least partially ionized plasma. To generate radiation efficiently, for example, 10 Pa of Xe, Li, Sn vapor, or other suitable gas or vapor partial pressure is required. In some embodiments, excited tin (Sn) is provided to generate EUV plasma.

[0044] Radiation emitted by the hot plasma 210 passes through an optional gas barrier or contaminant trap 230 (sometimes also referred to as a contaminant barrier or foil trap) located in or behind the opening of the source chamber 211. Then, it is sent from the radiation source chamber to the collector chamber 212. The contaminant trap 230 can include a channel structure. The contaminant trap 230 can further include a gas barrier or a combination of a gas barrier and a channel structure. The contaminant trap or contaminant barrier 230 further shown herein includes at least one channel structure as is known in the art.

[0045] The collector chamber 211 may include a radiation collector CO, which may be a grazing incidence collector. The radiation collector CO has an upstream radiation collector side 251 and a downstream radiation collector side 252. Radiation traversing the collector CO can be reflected from the diffraction grating spectral filter 240 and focused on the virtual source point IF. The virtual source point IF, also called the intermediate focus, and the source collector module are arranged so that the intermediate focus IF is located at or near the opening in the closure structure 220. The virtual radiation source point IF is an image of the radiation emission plasma 210.

[0046] Thereafter, the radiation provides a desired angular distribution of the radiation beam 21 at the patterning device MA and a desired uniformity of radiation intensity at the patterning device MA, Across an illumination system IL that may include a pupil mirror device 24. When the radiation beam 21 is reflected by the patterning device MA held by the support structure MT, a patterned beam 26 is formed, which is passed by the projection system PS via the reflective element 28 to the wafer stage or substrate table WT. The image is formed on the substrate W held by.

[0047] The illumination optical unit IL and the projection system PS may generally have more elements than shown. Depending on the type of lithographic apparatus, an optional diffraction grating spectral filter 240 may be provided. In addition, there may be additional mirrors beyond that shown, for example, 1-6 additional reflective elements beyond those shown in FIG. 2 may be provided in the projection system PS.

The collector optical system CO as shown in FIG. 2 is shown as a nested collector having grazing incidence reflectors 253, 254, and 255 as an example of a collector (or collector mirror). The grazing incidence reflectors 253, 254, and 255 are arranged axisymmetrically about the optical axis O, and this type of collector optics CO is preferably used in combination with a discharge generated plasma source often referred to as a DPP source. .

[0049] In an embodiment of the present invention, the source collector module SO may be part of an LPP radiation system, as shown in FIG. Laser LA absorbs laser energy in a fuel such as xenon (Xe), tin (Sn), or lithium (Li) to produce highly ionized plasma 210 having an electron temperature of tens of electron volts. The energy radiation generated during de-excitation and recombination of these ions is emitted from the plasma, collected by the near normal incidence collector optics CO, and focused into the opening 221 in the closure structure 220.

[0050] According to an embodiment of the invention, Fig. 4 shows an arrangement for an EUV lithographic apparatus in which the spectral purity filter SPF is a transmissive diffraction grating rather than a reflective diffraction grating. In this case, radiation from the radiation source follows a straight path from the collector to the intermediate focus IF (virtual radiation source point). In an alternative embodiment (not shown), the spectral purity filter 11 can be placed at the virtual source point 12 or at any location between the collector 10 and the virtual source point 12. The filter can also be arranged at another position in the radiation path, for example downstream of the virtual radiation source point 12. A plurality of filters can be arranged. Similar to the above example, the collector CO may be of a grazing incidence type (FIG. 2) or a direct deflector type (FIG. 3).

[0051] As described above, a contaminant trap 230 including a gas barrier is provided in the radiation source chamber. The gas barrier includes a channel structure as described, for example, in US Pat. No. 6,614,505 and US Pat. No. 6,359,969, which are hereby incorporated by reference in their entirety. The purpose of the contaminant trap is to prevent or at least reduce the generation of fuel material or by-products that impinge on the elements of the optics and the deterioration of these elements over time. The gas barrier may act as a physical barrier (by backflow of fluid), by chemical reaction with contaminants, and / or by electrostatic or electromagnetic deflection of charged particles. In practice, a combination of these methods may be used to transmit radiation to the illumination system while blocking the plasma material to the maximum possible extent. As described in the above US patent, hydrogen radicals can be injected into the particles to chemically modify Sn or other plasma materials. Hydrogen radicals can also be used to clean Sn and other elements that may already be deposited on the optical surface.

[0052] Hydrogen or other gas may be provided as a barrier or buffer against contaminant particles elsewhere in the lithographic apparatus. In particular, a flow of hydrogen into the source chamber SO can be prepared to prevent particles that may attempt to pass through the intermediate focus aperture 221. In addition, hydrogen gas (i) as a buffer for contaminants from systems that contaminate the reticle, in the vicinity of the reticle support MT, and (ii) as a buffer for contaminants from wafers that enter a larger vacuum space within the system. It can be deployed in the vicinity of the wafer support.

[0053] For all these purposes, a hydrogen source HS (some are shown and some are not shown) is deployed for hydrogen gas to each contaminant trap arrangement. One source may supply molecular hydrogen gas (H ₂ ) as a simple buffer, and another source generates hydrogen radicals.

[0054] US Pat. No. 6,781,673 (“the '673 patent”), which is incorporated herein by reference in its entirety and proposes electrostatic deflection to protect the reticle. Yes. The same principle can be applied to other components and spaces of the lithographic apparatus. The '673 patent proposes charging the particles using the electrostatic effect of the EUV beam itself, which generates a positive charge on the tin particles.

[0055] According to certain embodiments of the present invention, FIG. 5 depicts a system for removing contaminant particles from a path of an EUV radiation beam in a lithographic apparatus according to certain embodiments of the present invention. In this arrangement, the system for removing contaminant particles is in the region of the lithographic apparatus where the EUV radiation beam 30 is supplied by the illumination system IL and is incident on the patterning device MA, where the patterned EUV radiation beam is directed to the projection system PS. Provided.

[0056] As described above, and as shown in FIG. 5, hydrogen is supplied to both the illumination system IL and the projection system PS, so that from the illumination system IL and the projection system PS to the patterning device MA, respectively. Hydrogen flows 32, 33 are produced. In particular, the hydrogen flow 32 from the illumination system IL may be accompanied by contaminating particles, for example from a radiation source SO. Therefore, it is desirable to prevent such contaminant particles 35 from reaching the patterning device MA. For example, particles as small as 20 nm deposited on the patterning device MA can cause fatal defects in all dies subsequently formed on the substrate.

[0057] In the contaminant particle removal system of the present invention, a pair of electrodes 41, 42 can be provided on either side of the path of the EUV radiation beam. As shown in FIG. 5, the electrodes 41, 42 can be placed on either side of the EUV radiation beam in the vicinity of the patterning device MA, so that a pair of electrodes 41, 42 are both supplied by the illumination system IL. Located on opposite sides of the EUV radiation beam and on either side of the EUV radiation beam directed from the patterning device MA to the projection system PS.

A controlled voltage is set between the pair of electrodes 41 and 42 in the same manner as the system for removing contaminant particles that has been proposed so far. Therefore, electrostatically charged contaminant particles can be attracted to one electrode 42 and removed from the EUV radiation beam path.

[0059] In one embodiment, one electrode 41 can be grounded and the other electrode 42 applied with a positive voltage to attract negatively charged particles thereto. However, it will be understood that either electrode 41, 42 may be grounded and a voltage applied to the other. Further, in an alternative embodiment, a positive voltage is applied to one of the electrodes 41, 42, and a negative voltage is applied to the other electrode 41, 42, to obtain a desired voltage between the pair of electrodes 41, 42. A difference can be provided. Such an arrangement has the advantage that the electric field is better confined in the space between the pair of electrodes 41, 42 because the other surface in the vicinity of the electrodes 41, 42 can be grounded. .

[0060] However, unlike previously proposed electrostatic contaminant removal systems, the present invention includes a controller 45 configured to control a voltage source to provide a particular voltage regime. Yes. The performance of the system to remove contaminant particles by carefully selecting the voltage regime applied to the pair of electrodes 41, 42, for example, as compared to a system that supplies a constant DC voltage to the pair of electrodes 41, 42. Improvement is obtained.

[0061] As described above, electrostatic contaminant removal systems that have been proposed so far have been based on utilizing the photoelectric effect of the EUV beam to impart a positive charge to the contaminant particles. However, the presence of hydrogen gas results in the formation of a conductive hydrogen plasma by EUV radiation. This plasma may shield the contaminant particles from the electrostatic field generated by the voltage difference between the electrodes 41, 42. In addition, hydrogen plasma can gradually add negative charges to contaminating particles, erasing positive charges with photoelectric effects. Certain embodiments of the present invention are based on the recognition that by providing an elaborate voltage regime with electrodes 41, 42, the performance of the system can be enhanced.

[0062] In particular, certain embodiments of the present invention include a first stage in which an AC voltage is supplied to the pair of electrodes 41, 42, and a second stage in which a DC voltage is supplied to the pair of electrodes 41, 42. A voltage regime including a stage may be used.

[0063] The first stage of the regime serves to draw charged contaminating particles 35 into one of the electrodes 41, 42, similar to previously proposed systems. The first stage is provided to interact with hydrogen plasma formation to enhance the performance of the second stage.

[0064] In some embodiments of the invention, the AC voltage of the first stage is selected to increase the density of the hydrogen plasma generated by the EUV radiation beam. In such an embodiment, the plasma density increase may be sufficient to cause the contaminant particles 35 to be relatively strong and negatively charged, ie more than compensate for the positive charge of the photoelectric effect. . Increasing the intensity of the net charge on the contaminating particles 35 increases the probability that the individual particles 35 are sufficiently deflected from their original trajectory by the second stage voltage at which the individual particles 35 are captured by the electrode 42. Can do.

[0065] In another embodiment of the present invention, the AC voltage of the first stage is such that the AC voltage supplied between the pair of electrodes 41, 42 dissipates the hydrogen plasma generated by the EUV radiation beam. have.

[0066] In any case, it should be understood that the hydrogen plasma formed by EUV radiation will naturally dissipate over time. However, by appropriately selecting the AC voltage of the first stage, the hydrogen plasma can be dissipated more quickly than it naturally dissipates. Therefore, the shielding action of hydrogen plasma can be removed or reduced during the second stage. Therefore, when a predetermined charge is applied to the contaminating particle 35, the effect of the DC voltage applied to the electrodes 41 and 42 in the second stage becomes larger. On the other hand, it increases the probability that certain contaminant particles 35 are attracted to the electrode 42.

[0067] In yet another arrangement of voltage regimes used in certain embodiments of the invention, an intermediate stage in which an AC voltage is supplied to the electrodes 41, 42 may be provided. In such an arrangement, as described above, the AC voltage of the first stage can be selected to increase the plasma density of the hydrogen plasma generated by the EUV beam. The AC voltage of the intermediate stage may then be selected to dissipate the plasma more quickly than natural dissipation.

[0068] Thus, in such an arrangement, the system can advantageously utilize the first stage to increase the density of the plasma and thus increase the strength of the electrostatic charge applied to the contaminant particles 35. Thereafter, the intermediate stage increases the rate of plasma dissipation so that the shielding effect of the plasma is removed or reduced before the second stage where a DC voltage is used to attract the contaminant particles 35 to one electrode 42. Good.

[0069] As described above, in one embodiment of the system for removing contaminant particles according to this embodiment, the voltage required at each stage of the voltage regime is supplied between a pair of electrodes 41, 42 in a continuous period. Is done. In particular, the EUV radiation beam may be supplied by a pulsed radiation source. Therefore, the controller 45 can be configured to supply the necessary regime and voltage in synchronization with the pulse of the EUV radiation beam.

[0070] In particular, the sum of the duration of each stage of the voltage regime may correspond to the time between the start of successive pulses of the EUV radiation beam.

[0071] In an embodiment of the present invention, it may comprise a second stage of voltage regime, ie a supply stage of DC voltage, immediately before a subsequent pulse of EUV radiation, in particular a period between successive pulses of the EUV radiation beam. it can.

[0072] If the AC voltage of the first stage of the voltage regime is selected to concentrate the plasma density, the timing of this AC voltage is determined by the EUV radiation pulse and / or the period immediately after the EUV radiation pulse. Can match.

[0073] The timing of the regime stage that is configured such that the AC voltage dissipates the plasma can be slightly after the pulse of EUV radiation. If the first stage of the regime is also used to concentrate the plasma density, an intermediate stage configured to dissipate the plasma may follow immediately after the first stage or slightly later.

[0074] In a lithographic apparatus using an EUV pulsed radiation source, the pulse frequency can be, for example, 50 kHz, so that the pulse period, ie the time between the start of successive pulses of the EUV radiation beam, is 20 μs. It will be appreciated that other pulse frequencies may be used, such as 100 kHz and 200 kHz.

[0075] In general, it is desirable that the second stage, the regime stage supplying the DC voltage, last as long as possible to maximize the probability that the particles will be attracted to the voltage 42. In certain embodiments, the duration of the second stage of the voltage regime may be a duration corresponding to at least 40%, at least 50%, or at least 60% of the time between the start of successive pulses of the EUV radiation beam.

[0076] The voltage regime stage according to the invention used to increase the charge density of the plasma is preferably as short as possible. Such an arrangement is assisted by the AC voltage supplied in the intermediate stage of the voltage regime before the second stage where the DC voltage is supplied to attract the plasma naturally to dissipate or attract the charged contaminant particles 35. Give as much time as possible to dissipate. In certain embodiments of the invention, the duration of the voltage regime stage used to increase the plasma density is between 5-15% of the time between the start of successive pulses of the EUV radiation beam, desirably less than 10%. It may be.

[0077] The duration of the voltage regime stage according to the present invention used to assist in the dissipation of the plasma is desirably a DC voltage to attract charged contaminant particles to the electrode 42 prior to a subsequent pulse of the EUV radiation beam. There may be a sufficiently short period of time to leave sufficient time for the second stage of the supplied voltage regime. However, this period must also be long enough for the second stage to be effective, i.e., to sufficiently dissipate the plasma because the shielding action of the plasma is sufficiently mitigated. In some arrangements, such a stage of the voltage regime of the present invention may correspond to less than 30%, preferably less than 20% of the time between successive pulses of the EUV radiation beam.

[0078] When selecting the voltages used in the stages of the voltage regime used in the present invention, that is, the voltage magnitude and frequency, it is necessary to take into account the configuration of the system, including the geometry of the elements of the system. In particular, the following factors affect the selection of the voltage used.
The separation distance of the electrodes 41, 42, which determines the electric field strength together with the voltage applied to the electrodes 41, 42;
Predicted speed of contaminating particles 35 and their predicted mass range;
The length of the electrodes 41, 42 in the direction of travel of the contaminating particles, which determines the time that the particles can be in the space bounded by the electrodes 41, 42;
The pressure of hydrogen gas between the electrodes 41, 42 affecting the formation of plasma in the space between the electrodes 41, 42, the increase in plasma density obtained by the AC voltage, and the subsequent natural or assisted plasma dissipation. ,as well as,
EUV radiation beam timing and power.

[0079] When setting up the system of the present invention, it should be understood that contaminant particles can remain in the space bounded by the electrodes 41, 42 for the duration of multiple pulses of the EUV radiation beam. Thus, the system can be configured such that the contaminant particles 35 experience multiple cycles of a voltage regime corresponding to multiple pulses of the EUV radiation beam. Each cycle can increase the charge on the contaminating particles. For example, in an expected configuration of a lithographic apparatus with a pulse frequency of 50 kHz, the velocity of the contaminating particles may be approximately 20 m / s. In this case, for a pair of electrodes 41, 42, for example 60 mm in length, the particles 35 can remain between the electrodes 41, 42 for about 150 pulse periods of the EUV radiation beam.

[0080] Within each pulse, ie, during each cycle of the voltage regime, the net charge on the contaminant particle 35 may increase, and within each pulse a force is applied to the contaminant particle 35 during the second stage of the voltage regime. .

[0081] In a possible electrode 41, 42 configuration, the length of the electrode (ie, the length in the way that the contaminant particles are expected to travel) can be 60 mm, the width is about 100 mm, and probably about Will be separated by 40-90 mm. However, it will be understood that in general the electrodes are configured to be as wide as the EUV radiation beam and follow a shape as close as possible to the shape of the beam. The pressure of hydrogen in the space between the electrodes 41 and 42 may be about 3 Pa, for example.

[0082] In such an exemplary embodiment, the AC voltage selected for the voltage regime stage used to increase the density of the plasma generated by the EUV radiation beam is 20-100 MHz in frequency, The magnitude can be selected to be between 40-200V. Furthermore, the power supplied to the pair of electrodes 41, 42 in this voltage regime stage can be selected to be 0.005-0.04 W / cm ² based on the area of each electrode.

[0083] The AC voltage for the stage of the electrode regime used to promote plasma dissipation in the exemplary embodiment of the vapor has a frequency of 0.1-20 MHz, preferably about 10 MHz, and a voltage magnitude of 10-10. It can be selected to be 400V, preferably about 200V.

[0084] Finally, upon selection of the DC voltage used in the second stage of the voltage regime for the above exemplary embodiment, the DC voltage can be selected in the range of 100-400V, for example 200V.

[0085] In selecting a voltage to promote plasma dissipation and / or a voltage for the second stage of the voltage regime, the voltage magnitude must be selected to be a sufficiently low voltage that does not sustain the plasma. Please understand that. Thus, in a particular system configuration, the highest voltage that can be used for such a stage can be determined using a Paschen curve.

According to an embodiment of the present invention, FIGS. 6 and 7 include a system (FIG. 6) as shown in FIG. 5 in which a constant voltage of 200 V is applied to the electrodes 41 and 42, and a three-stage voltage regime. The results of the simulation using the resulting arrangement (FIG. 7) are compared. In particular, the regime includes a 40 V, 2 μs, 100 MHz first stage, a 400 V, 6 μs, 0.25 MHz intermediate stage, and a 12 μs, DC 400 V, second stage.

[0087] In both FIG. 6 and FIG. 7, the graphs show non-stop probability distributions by particle size at multiple different pulses where the particles remain in the space bounded by the electrodes 41, 42, ie the size of the electrodes and contamination The non-stop probability distribution corresponding to the difference in the basic configuration of the system including the predicted speed of particles is shown. As shown, the performance of the three stage voltage regime is significantly improved over a system using a DC constant voltage.

[0088] While the present invention has been described above in the context of the embodiment shown in FIG. 5, it should be understood that the present invention may be implemented in alternative embodiments. For example, as shown in FIG. 8, in accordance with an embodiment of the present invention, two pairs of electrodes 61, 62 may be provided with associated voltage controllers 63, 64, respectively.

[0089] For example, the voltage source 63 can be controlled by the controller 45 to supply the voltage required for the first stage of the voltage regime to the first pair of electrodes 61 and the second voltage source 64. May supply the second pair of electrodes 62 with the voltage required for the intermediate stage and the second stage of the voltage regime. In the first region between the first pair of electrodes 61, the contaminant particles are charged by a plasma that has increased in density as a result of the voltage applied to the first pair of electrodes 61 according to the first stage of this regime. Is done. Thereafter, in the space between the second pair of electrodes 62, a second stage of voltage regime, i.e., before a DC voltage is applied to the second pair of electrodes 62 to remove contaminant particles, the plasma is applied. An intermediate stage of a voltage regime is applied to the second pair of electrodes 62 for dissipation.

[0090] FIGS. 9 and 10 show the results of a simulation using a system as shown in FIG. 8 for different contaminant particles. Specifically, FIG. 9 illustrates the result of contaminating particles of a material having a relatively high secondary electron emission rate, such as a metal, according to an embodiment of the present invention. In particular, the secondary electron emission rate k is 0.02. FIG. 10 shows the result of a material having a relatively low secondary electron emission rate, such as an insulator, specifically, an insulator having k of 0.002. In both FIG. 9 and FIG. 10, the first stage of the voltage regime is supplied by the first pair of electrodes 61 using a voltage of 40V, 100 MHz and supplies 0.03 W / cm ² of power. The intermediate stage applied to the second pair of electrodes 62 is supplied by a voltage of 200 V, 10 MHz from the start of each 6.5 μs pulse of the EUV radiation beam. The second stage, also applied to the second pair of electrodes 62 from the end of the intermediate stage to the start of the next pulse of the EUV radiation beam, is DC 200V.

[0091] As shown in FIGS. 9 and 10, according to the embodiment of the present invention, the non-stop probability is significantly higher than that of a conventionally known system using a DC constant voltage, that is, a system as shown in FIG. To improve. However, in the embodiment as shown in FIG. 8, particles of different materials have different deceleration efficiencies.

[0092] Embodiments as shown in FIG. 8, ie, embodiments in which the first and second stages of the voltage regime are spatially separated, could be used for systems where a non-pulsed radiation beam is used. In such an arrangement, the first stage may be an AC voltage configured to increase the plasma density to promote charging of the contaminant particles by the plasma. The second stage of the voltage regime may be a DC voltage that is used to remove charged contaminant particles.

[0093] Although the text specifically refers to the use of a lithographic apparatus in the manufacture of ICs, it should be understood that the lithographic apparatus described herein has other uses. For example, this is the manufacture of integrated optical systems, guidance and detection patterns for magnetic domain memories, flat panel displays, liquid crystal displays (LCDs), thin film magnetic heads, and the like. In light of these alternative applications, the use of the terms “wafer” or “die” herein are considered synonymous with the more general terms “substrate” or “target portion”, respectively. Those skilled in the art will recognize that this may be the case. The substrates described herein may be processed before or after exposure, for example, with a track (usually a tool that applies a layer of resist to the substrate and develops the exposed resist), metrology tools, and / or inspection tools. be able to. Where appropriate, the disclosure herein may be applied to these and other substrate processing tools. In addition, the substrate can be processed multiple times, for example to produce a multi-layer IC, so the term substrate as used herein can also refer to a substrate that already contains multiple processed layers.

[0094] Although specific reference has been made to the use of embodiments of the present invention in the field of optical lithography, the present invention can be used in other fields, such as imprint lithography, depending on context, and is not limited to optical lithography. I want you to understand. In imprint lithography, the topography in the patterning device defines a pattern created on the substrate. The topography of the patterning device is imprinted in a resist layer applied to the substrate, and the resist is cured by applying electromagnetic radiation, heat, pressure, or a combination thereof. The patterning device is removed from the resist, leaving a pattern in it when the resist is cured.

[0095] The term "lens" can refer to any one or a combination of various types of optical components, including refractive, reflective, magnetic, electromagnetic and electrostatic optical components, as the situation allows.

[0096] While specific embodiments of the invention have been described above, it will be appreciated that the invention may be practiced otherwise than as described. For example, the present invention provides a computer program that includes one or more sequences of machine-readable instructions that describe a method as disclosed above, or a data storage medium (eg, semiconductor memory, etc.) that stores such a computer program. Magnetic or optical disk).

[0097] For example, software functions of a computer system including programming including executable code may be used to implement the above inspection method. The software code may be executable by a general purpose computer. In operation, codes and possibly associated data records may be stored in a general purpose computer platform. However, at other times, the software may be stored in another location and / or transferred for loading into an appropriate general purpose computer system. Accordingly, the above embodiments include one or more software in the form of one or more code modules mounted on at least one machine readable medium. Execution of such code by a processor of a computer system allows the platform to perform functions that are essentially similar to the functions described herein and performed in the illustrated embodiment.

[0098] The term computer or machine "readable medium" as used herein refers to any medium that participates in providing execution instructions to a processor. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks such as any storage device in any computer that operates as described above. Volatile media includes dynamic memory, such as the main memory of a computer system. Physical transmission media include coaxial cables, copper wires, and optical fibers, including wires that provide buses within a computer system. Carrier transmission media can take the form of electrical or electromagnetic signals, or acoustic or optical signals, such as those generated during radio frequency (RF) and infrared (IR) data communications. Thus, common forms of computer readable media include floppy disk, flexible disk, hard disk, magnetic tape, any other magnetic medium, CD-ROM, DVD, any other optical medium, punch card, paper tape, Generally less commonly used media such as any other physical media with a perforated pattern, RAM, PROM, and EPROM, FLASH-EPROM, any other memory chip or cartridge, carrier wave carrying data or instructions, such as Includes a cable or link that carries a carrier wave, or any other medium from which a computer can read or transmit programming code and / or data. Many of these forms of computer readable media may be involved in carrying to a processor to execute one or more sequences of one or more instructions.

[0099] Recognizing that in interpreting the claims, the section “Summary of Invention” and “Summary” is intended to use the “Mode for Carrying Out the Invention” section. I want to be. While the "Summary" and "Summary" sections may describe one or more exemplary embodiments of the invention as contemplated by the inventors, it is not intended to describe all exemplary embodiments. Therefore, it is not intended to limit the invention and the appended claims in any way.

[00100] The present invention has been described above using functional configuration storage elements and their relationships that exemplify embodiments of specific functions. The boundaries of these functional configuration storage elements are arbitrarily defined herein for convenience of explanation. Alternative boundaries can be defined as long as certain functions and their relationships are properly performed.

[00101] The foregoing description of specific embodiments sufficiently clarifies the overall nature of the present invention, so that by applying the knowledge in the art, without undue experimentation, Such particular embodiments can be readily modified and / or adapted to various applications without departing from the general concept. Accordingly, such adaptations and modifications are intended to fall within the meaning and scope of the equivalents of the disclosed embodiments based on the teachings and guidance presented herein. The terminology or terminology herein is for the purpose of description, not limitation, and thus the terminology or terminology herein should be construed in terms of teaching and guidance to those skilled in the art. I want you to understand.

[00102] The breadth and scope of the present invention are not limited by any of the above-described exemplary embodiments, but are defined only by the claims and their equivalents.

Claims (28)

A system for removing contaminant particles from a path of an EUV radiation beam in a lithographic apparatus,
(A) at least one pair of electrodes provided on opposite sides of the path of the EUV radiation beam;
(B) a voltage source for supplying a controlled voltage between the at least one pair of electrodes;
(C) a controller for controlling a voltage supplied between the at least one pair of electrodes;
The controller supplies a voltage regime between the at least one pair of electrodes, the regime being supplied with a first stage in which an AC voltage is supplied to the pair of electrodes and a DC voltage supplied to the pair of electrodes. And a second stage.   The system for removing contaminant particles according to claim 1, wherein the required voltage of each stage of the regime is provided between the same pair of electrodes in each successive period.   The EUV radiation beam is provided by a pulsed radiation source and the controller is configured such that the sum of the durations of the voltage regime stages corresponds to the time between the start of successive pulses of the EUV radiation beam. A system for removing contaminant particles according to claim 2.   The frequency and potential of the AC voltage of the first stage is selected with respect to the configuration of the system such that the AC voltage supplied between the pair of electrodes increases the density of the plasma produced by the EUV radiation beam. The system for removing contaminant particles according to claim 2 or 3.   The system for removing contaminant particles according to claim 4, wherein the frequency of the AC voltage of the first stage is between 20 and 100 MHz.   The system for removing contaminant particles according to claim 4 or 5, wherein the magnitude of the AC voltage of the first stage is between 40 and 200V. System power supplied to the electrodes of the pair, which is between 0.005~0.04W / cm ^2, for removing contaminant particles as set forth in any one of claims 4 6 by an AC voltage.   The frequency and magnitude of the AC voltage of the first stage is selected such that the AC voltage supplied between the pair of electrodes dissipates the plasma generated by the EUV radiation beam with respect to the system configuration. The system for removing contaminant particles according to claim 2 or 3.   9. The system for removing contaminant particles according to claim 8, wherein the frequency of the AC voltage of the first stage is between 0.1 and 20 MHz, preferably 10 MHz.   The system for removing contaminant particles according to claim 8 or 9, wherein the magnitude of the AC voltage of the first stage is between 10 and 400V, preferably 200V. The voltage regime includes an intermediate stage provided between the first stage and the second stage in which an AC voltage is supplied to a pair of electrodes,
The system for removing contaminant particles according to claim 3, wherein the frequency of the AC voltage of the first stage is higher than the frequency of the AC voltage of the intermediate stage.   The frequency and magnitude of the AC voltage of the first stage and the intermediate stage is determined with respect to the configuration of the system by determining whether the AC voltage supplied between the pair of electrodes of the first stage is the EUV radiation beam. The contaminant particles of claim 11, wherein the plasma voltage generated by the second stage is selected such that the AC voltage supplied between the pair of electrodes of the second stage dissipates the plasma. The system to remove.   The system for removing contaminant particles according to claim 12, wherein the frequency of the AC voltage of the first stage is between 20 and 100 MHz.   14. The system for removing contaminant particles according to claim 12 or 13, wherein the magnitude of the AC voltage of the first stage is between 40-200V. The power supplied to the electrodes of the pair by the AC voltage of the first stage is between 0.005~0.04W / cm ^2, according to any one of claims 12 to 14 A system that removes contaminant particles.   16. A system for removing contaminant particles according to any one of claims 12 to 15, wherein the frequency of the AC voltage of the intermediate stage is between 0.1 and 20 MHz, preferably 10 MHz.   17. A system for removing contaminant particles according to any one of claims 12 to 16, wherein the AC voltage of the intermediate stage is between 10 and 400V, preferably 200V.   18. The period of the first stage of the regime corresponds to between 5 and 15% of the time between the start of successive pulses of the EUV radiation beam, preferably less than 10%. A system for removing contaminant particles according to any one of the preceding claims.   19. The period of the intermediate stage of the regime corresponds to less than 30% of the time between the start of successive pulses of the EUV radiation beam, preferably less than 20%. A system for removing contaminant particles described in 1.     20. The period of the second stage of the regime corresponds to at least 40%, at least 50%, or at least 60% of the time between the start of successive pulses of the EUV radiation beam. A system for removing contaminant particles according to item 1. The at least one pair of electrodes are provided at respective positions along an axis of the EUV radiation beam such that the first pair of electrodes is closer to the source of contaminant particles than the second pair of electrodes. A second pair of electrodes;
The voltage of the first stage of the voltage regime is applied to the first pair of electrodes, and the voltage of the second stage of the electrode regime is applied to the second pair of electrodes. Item 4. A system for removing contaminant particles according to Item 1. The voltage regime includes an intermediate stage provided between the first stage and the second stage, wherein an AC voltage is supplied to a pair of electrodes;
The system for removing contaminant particles according to claim 21, wherein the AC voltage of the first stage is higher than the AC voltage of the intermediate stage.   23. The system for removing contaminant particles according to claim 22, wherein the voltage required for the intermediate stage and the second stage of the regime is supplied between the second pair of electrodes in each successive period.   24. The system for removing contaminant particles according to any one of claims 1 to 23, wherein the DC voltage of the second stage is selected from the range of 100-400V, and preferably 200V.   A lithographic apparatus comprising a system for removing contaminant particles according to any one of the preceding claims.   26. The system for removing contaminant particles of claim 25, wherein the system for removing contaminant particles removes contaminant particles from the EUV beam path between an illumination system and a patterning device that patterns the radiation beam. Lithographic apparatus. A method for removing contaminant particles from a path of an EUV radiation beam in a lithographic apparatus, comprising:
Providing at least one pair of electrodes on opposite sides of the path of the EUV radiation beam;
Providing a voltage regime between the at least one pair of electrodes;
And wherein the regime includes a first stage in which an AC voltage is applied to the pair of electrodes and a second stage in which a DC voltage is applied to the electrodes.   28. A device manufacturing method comprising projecting a patterned EUV radiation beam onto a substrate, the method comprising using a method according to claim 27, wherein contaminant particles are removed from at least a portion of a path of the EUV radiation beam. Device manufacturing method.